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Improve the use of English in comments #2

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merged 1 commit into from
Feb 24, 2023
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tomhukins
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Thank you for all your work on ZFS block cloning. It looks like a beneficial feature that I look forward to using.

I found your comments descriptive, informative and easy to read, but as a native English speaker I found the wording awkward in a few places so I thought I should send you this small patch.

@pjd pjd merged commit 6c144c1 into pjd:brt Feb 24, 2023
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pjd commented Feb 24, 2023

Thank you!

pjd pushed a commit that referenced this pull request Feb 24, 2023
Under certain loads, the following panic is hit:

    panic: page fault
    KDB: stack backtrace:
    #0 0xffffffff805db025 at kdb_backtrace+0x65
    #1 0xffffffff8058e86f at vpanic+0x17f
    #2 0xffffffff8058e6e3 at panic+0x43
    openzfs#3 0xffffffff808adc15 at trap_fatal+0x385
    openzfs#4 0xffffffff808adc6f at trap_pfault+0x4f
    openzfs#5 0xffffffff80886da8 at calltrap+0x8
    openzfs#6 0xffffffff80669186 at vgonel+0x186
    openzfs#7 0xffffffff80669841 at vgone+0x31
    openzfs#8 0xffffffff8065806d at vfs_hash_insert+0x26d
    openzfs#9 0xffffffff81a39069 at sfs_vgetx+0x149
    openzfs#10 0xffffffff81a39c54 at zfsctl_snapdir_lookup+0x1e4
    openzfs#11 0xffffffff8065a28c at lookup+0x45c
    openzfs#12 0xffffffff806594b9 at namei+0x259
    openzfs#13 0xffffffff80676a33 at kern_statat+0xf3
    openzfs#14 0xffffffff8067712f at sys_fstatat+0x2f
    openzfs#15 0xffffffff808ae50c at amd64_syscall+0x10c
    openzfs#16 0xffffffff808876bb at fast_syscall_common+0xf8

The page fault occurs because vgonel() will call VOP_CLOSE() for active
vnodes. For this reason, define vop_close for zfsctl_ops_snapshot. While
here, define vop_open for consistency.

After adding the necessary vop, the bug progresses to the following
panic:

    panic: VERIFY3(vrecycle(vp) == 1) failed (0 == 1)
    cpuid = 17
    KDB: stack backtrace:
    #0 0xffffffff805e29c5 at kdb_backtrace+0x65
    #1 0xffffffff8059620f at vpanic+0x17f
    #2 0xffffffff81a27f4a at spl_panic+0x3a
    openzfs#3 0xffffffff81a3a4d0 at zfsctl_snapshot_inactive+0x40
    openzfs#4 0xffffffff8066fdee at vinactivef+0xde
    openzfs#5 0xffffffff80670b8a at vgonel+0x1ea
    openzfs#6 0xffffffff806711e1 at vgone+0x31
    openzfs#7 0xffffffff8065fa0d at vfs_hash_insert+0x26d
    openzfs#8 0xffffffff81a39069 at sfs_vgetx+0x149
    openzfs#9 0xffffffff81a39c54 at zfsctl_snapdir_lookup+0x1e4
    openzfs#10 0xffffffff80661c2c at lookup+0x45c
    openzfs#11 0xffffffff80660e59 at namei+0x259
    openzfs#12 0xffffffff8067e3d3 at kern_statat+0xf3
    openzfs#13 0xffffffff8067eacf at sys_fstatat+0x2f
    openzfs#14 0xffffffff808b5ecc at amd64_syscall+0x10c
    openzfs#15 0xffffffff8088f07b at fast_syscall_common+0xf8

This is caused by a race condition that can occur when allocating a new
vnode and adding that vnode to the vfs hash. If the newly created vnode
loses the race when being inserted into the vfs hash, it will not be
recycled as its usecount is greater than zero, hitting the above
assertion.

Fix this by dropping the assertion.

FreeBSD-issue: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252700
Reviewed-by: Andriy Gapon <[email protected]>
Reviewed-by: Mateusz Guzik <[email protected]>
Reviewed-by: Alek Pinchuk <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Rob Wing <[email protected]>
Co-authored-by: Rob Wing <[email protected]>
Submitted-by: Klara, Inc.
Sponsored-by: rsync.net
Closes openzfs#14501
pjd added a commit that referenced this pull request Feb 26, 2023
- Update the comment about scrub interaction with BRT.
- Use com.fudosecurity for consistency with feature flags.
- Do the light checks first and move brt_maybe_exists() at the end.

Signed-off-by: Pawel Jakub Dawidek <[email protected]>
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2 participants